Current trends within print head design involve increasing the jet packing density and jet count while simultaneously reducing the cost of the print head. The ‘jets,’ also referred to as nozzles, drop emitters or ejection ports, generally consist of apertures or holes in a plate through which ink is expelled onto a print surface. Higher density and higher counts of jets results in higher resolution and higher quality print images.
Each jet has a corresponding actuator, some sort of transducer that translates an electrical signal to a mechanical force that causes ink to exit the jet. The electrical signals generally result from image data and a print controller that dictates which jets need to expel ink during which intervals to form the desired image. Examples of transducers include piezoelectric transducers, electromechanical transducers, heat generating elements such as those that cause bubbles in the ink for ‘bubble jet’ printers, etc.
Some of the transducer elements act against a membrane that resides behind the ‘jet stack,’ a series of plates through which ink is transferred to the nozzle or jet plate. The actuation of the transducers causes the membrane to push against the chambers of the jet stack and ultimately force ink out of the nozzles.
The increased jet packing density and jet count introduce the need for significant reductions in the size and spacing between the actuators, electrical traces, and electromechanical interconnects. The electromechanical interconnect of the most interest here forms the interconnect between the single jet actuators and their corresponding drive electronics through which they receive the signals mentioned above. Current methods make the interconnect between the drive circuitry and the transducers/actuators expensive, and may not have the capability of achieving manufacturable and reliable interconnects at the increased density and reduced sizes desired. Some potential solutions include chip on flex (COF) and tape automated bonding (TAB) technologies where the driving circuitry resides on flexible substrates.